A portable device such as a portable folder-type radiotelephone includes two case units coupled to each other through a hinge device. Usually, one unit is provided with a keypad with buttons, and the other unit is provided with a liquid crystal display. When the radiotelephone is in use, the keypad and the liquid crystal display are moved to an unfolded position of the radiotelephone so that the keypad and display can be exposed to the outside. The hinge device allows the two units to be coupled to each other and to be smoothly moved to folded and unfolded positions of the radiotelephone.
A typical hinge device is constructed as follows. The hinge device comprises a rotating member, a linearly moving member, a resilient member, and a housing. The housing contains the rotating member, the linearly moving member and the resilient member. The rotating member can rotate about a rotation axis within the housing, and a portion of the rotating member protrudes outside of the housing to form a coupling portion. The linearly moving member is in contact with the rotating member, and does not rotate within the housing but moves linearly along a rotational shaft of the housing. The resilient member applies a force so that the linearly moving member and the rotating member can be brought into close contact with each other within the housing. At this time, contact surfaces of the linearly moving member and the rotating member are properly configured such that the rotating member easily rotates even without an external force in a certain range and is well maintained in a stationary state at a predetermined location.
One of two case units of a portable radiotelephone that are intended to be coupled to the hinge device constructed as above is fixed to the housing while the other is fixed to the coupling portion of the rotating member. The two units of the portable radiotelephone thus connected are maintained in the stationary state when they are at an unfolded or folded position of the radiotelephone through the operation of the hinge device. Further, in order to move the two units, which have been at the unfolded position or folded position of the radiotelephone, to the folded or unfolded position, a user should initially apply an external force to the two units with his/her hand in a certain range. In a range subsequent to the certain range, the two units are generally automatically moved to the folded or unfolded position.
However, the two case units of the portable folder-type radiotelephone with the hinge device constructed as above are difficult to move to the unfolded position through 180 or more degrees. Even though such movement of the two units may be established, the two units are not placed in the same plane or a portion of the two units protrudes from a plane due to the structure of the hinge device.